1. Field of the Invention
The present invention relates to an image recognition apparatus, a control method for an image recognition apparatus, and a storage medium.
2. Description of the Related Art
Conventionally, there is a known technique to extract a face region from an image including a human face and recognize a facial expression by analyzing the extracted face region. Application of this technique to an imaging apparatus allows recording a face image when a person captured by the imaging apparatus smiles, and recording a face image when the person's line of sight is directed toward a camera.
A technique to recognize a facial expression using LBP histograms generated from local binary patterns (LBP) extracted from a luminance image is proposed in C. Shan and T. Gritti, “Learning Discriminative LBP-Histogram Bins for Facial Expression Recognition”, Proc. British Machine Vision. Conference, 2008. The technique proposed in C. Shan and T. Gritti, “Learning Discriminative LBP-Histogram Bins for Facial Expression Recognition”, Proc. British Machine Vision. Conference, 2008, is intended to improve robustness by absorbing misalignment of an object in an image with the use of histogram features.
However, in general, histogram features have many dimensions. This is problematic because the more dimensions of features there are, the larger the processing load on a discriminator. In the case where LBP histograms or luminance gradient histograms are used as features, the larger the number of histogram bins, the more dimensions of generated features there are, and the larger the processing load on a discriminator. Furthermore, bins that are easily affected by noise may cause false recognition.